Lubricant for chain conveyor belts and its use

ABSTRACT

Chain conveyor lubricants, especially for the food industry, which form clear solutions in water and which contain in combination 
     a) at least one compound corresponding to formula (I):                    
      in which 
     R 1  is a saturated or mono- or polyunsaturated, linear or branched alkyl group containing 6 to 22 carbon atoms, which may optionally be substituted by an —OH, —NH 2 , —NH—, —CO—, halogen or a carboxyl group, 
     R 2  is a carboxyl group containing 2 to 7 carbon atoms, 
     M is hydrogen, alkali metal, ammonium, an alkyl group containing 1 to 4 carbon atoms or a benzyl group, and 
     n is an integer of 1 to 6; 
     b) at least one organic carboxylic acid selected from monobasic or polybasic, saturated or mono- or polyunsaturated carboxylic acids containing 2 to 22 carbon atoms; and, optionally, 
     c) at least one of water, additives, and auxiliaries.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to chain conveyor lubricants which form clearsolutions in water and which contain amphoteric compounds correspondingto general formula (I), organic carboxylic acids and, optionally, waterand additives and/or auxiliaries.

The invention also relates to the use of such lubricant combinations aschain conveyor lubricants in the food industry. More particularly, thelubricants according to the invention are used for lubricating, cleaningand disinfecting automatic chain conveyors of the type used in thepackaging of foods, preferably beverages, in glass and plastic bottles,cans, glasses, barrels, kegs, paper and cardboard containers and thelike.

2. Statement of Related Art

In bottle cellars and barrel cellars of beverage factories and in thepackaging of foods, plate-type conveyor belts or chain conveyors arenormally used for transporting the corresponding vessels, beinglubricated and kept clean with suitable water-based lubricantpreparations applied by dip lubrication or by automatic belt lubricationsystems.

Whereas, in dip lubrication systems, the choice of the lubricant doesnot present any problems so far as performance properties are concerned,the precipitation of poorly soluble salts together with microbiologicaldeposits in the nozzles and filters of centralized lubrication systemscan seriously affect the continuous packaging of foods, particularlybeverages, so that the systems always have to be switched off andcleaned after a certain period of operation.

The chain lubricants hitherto used for lubrication are based on the onehand on fatty acids in the form of their water-soluble alkali metal oralkanolamine salts or on fatty amines in the form of their organic orinorganic salts.

DE-A-23 13 330 describes soap-based lubricants containing aqueousmixtures of C₁₆₋₁₈ fatty acid salts and surfactants.

Apart from these soap-based lubricants, lubricants based on primaryfatty amines are otherwise mainly used. Thus, DE-A-36 31 953 describes aprocess for lubricating chain-type bottle conveyors in bottling plants,more particularly in breweries, and for cleaning the conveyors with aliquid cleaner which is characterized in that the chain-type bottleconveyors are lubricated with conveyor lubricants based on neutralizedprimary fatty amines which preferably contain 12 to 18 carbon atoms andan unsaturated component of more than 10% and in that the bottleconveyors are cleaned with cationic cleaning preparations based on thequaternary ammonium compounds, such as alkyl trimethyl ammoniumchloride, dialkyl dimethyl ammonium chloride and alkyl dimethyl benzylammonium chloride, or organic acids.

The main disadvantages of these fatty amines are: the reaction withanions present in the water, more particularly sulfates, bicarbonates,phosphates and carbonates from alkaline waters and other wateringredients; a strong reaction with carbonic acid dissolved in water toform poorly soluble ammonium carbonates, for example in the case ofbeverages containing carbon dioxide; solubilizers have to be used; thespraying and distribution system has to be cleaned at regular intervals;otherwise the system as a whole blocks up and thus becomes unusable.

In the case of lubricants based on primary fatty amines, continuous24-hour operation is not possible. Where primary fatty amines are usedas lubricants, the plants can only be operated with minimal flexibility;in many cases, this process cannot be applied at all because premixingtanks are often present in existing plants. The use of primary fattyamines and the two process steps which it entails—on the one handlubrication, on the other hand cleaning—involves high capital investmenton equipment. Finally, the use of primary amines and loweralkanecarboxylic acids (for example acetic acid), which are necessaryfor the cleaning step, is accompanied by serious odor emission.

Accordingly, the main disadvantages of the processes mentioned above lieon the one hand in the marked dependence on water of the soap-basedlubricants and in the need for regular cleaning of the system wherelubricants based on primary amines are used. The precipitationsencountered in both known processes have to be removed at the same time.A simple acid/base reaction is used for this purpose. In the case ofsoap products based on fatty acids, alkaline cleaners containingcomplexing agents are used for this reaction; in the case of productsbased on primary fatty amines, organic or inorganic acids are used astechnical equivalents to perform the cleaning function.

Finally, chain lubricants without any of the disadvantages mentionedabove are known from the prior art. Thus, EP-A-0 044 458 describeslubricant preparations which are substantially free from fatty acidsoaps and which in addition contain a carboxylated nonionic surfactantand an acyl sarcosinate. The pH value of these products is in the rangefrom 7 to 11 and, accordingly, is preferably in the neutral to alkalinerange.

Finally, DE-A-38 31 448 relates to water-containing, soapless lubricantpreparations which form clear solutions in water, to a process for theirproduction and to their use in particular as lubricants for thetransport of glass bottles or polyethylene terephthalate bottles. Thesubstantially neutral water-containing lubricant preparations (pH 6 to8) contain alkyl benzenesulfonates, alkoxylated alkanol phosphates andalkanecarboxylic acids, optionally in addition to typical solubilizers,solvents, foam inhibitors and disinfectants.

Unfortunately, the two products described above are attended by thefollowing three disadvantages:

1. They are microbiologically unfavorable because they create excellentgrowth conditions for micro-organisms.

2. In addition, they show minimal cleaning power.

3. Finally, their foaming behavior is difficult to control.

DE-A-39 05 548 describes lubricants containing at least one secondaryand/or tertiary amine and/or salts of such amines. Unfortunately, theseconveyor hygiene products have been found in practice to exhibit certainproblems on account of the skin irritation observed in a few cases whichwas attributed to these products and on account of the formation oftoxic secondary products in the event of careless handling(alkalization). On account of their poor wetting effect, thesehydrophobic compounds can only be used in the optimal operational stateof a conveyor lubrication system. The compounds are neutralized byorganic impurities or acids, for example by the introduction ofphosphate.

U.S. Pat. No. 3,574,100 describes lubricant compositions containingamphoteric compounds which are named in this document as N-fattyalkyl-β-aminopropionates and N-fatty alkyl-β-iminodipropionates.

However, where these compounds are used in lubricants, relative highfriction coefficients are observed.

In addition, their ability to form clear solutions in water isinadequate for use in centralized lubrication systems in the foodindustry, more particularly permanently installed automatic systems.

DESCRIPTION OF THE INVENTION

Accordingly, the problem addressed by the present invention was toprovide new improved lubricant preparations, more particularly chainconveyor lubricants forming clear solutions in water, which would not beattended by the disadvantages of the prior art. The lubricants accordingto the invention have a good coefficient of friction, i.e. an excellentlubricating effect, generate little foam and combine an excellentcleaning effect with high microbicidal activity.

The present invention relates to chain conveyor lubricants forming clearsolutions in water and containing in combination

a) at least one compound corresponding to general formula (I):

 in which

R¹ is a saturated or mono- or polyunsaturated, linear or branched alkylgroup containing 6 to 22 carbon atoms which may optionally besubstituted by —OH, —NH2, —NH—, —CO—, halogen or a carboxyl group,

R² is a carboxyl group containing 2 to 7 carbon atoms,

M is hydrogen, alkali metal, ammonium, an alkyl group containing 1 to 4carbon atoms or a benzyl group and

n is an integer of 1 to 6,

b) at least one organic carboxylic acid selected from monobasic orpolybasic, saturated or mono- or polyunsaturated carboxylic acidscontaining 2 to 22 carbon atoms,

c) optionally water and additives and/or auxiliaries.

A chain conveyor lubricant with excellent properties is obtained throughthe combination of amphoteric surfactant and organic carboxylic acid.The lubricating effect with friction coefficients μ of 0.12 or lower isdistinctly improved by comparison with amphoteric compounds on theirown.

The in-use solution can be adjusted to a high pH value. The chainconveyor lubricants according to the invention are not dependent onwater quality. In normal in-use concentrations, the lubricantcombinations generate very little foam. Particularly favorable resultswere obtained in the evaluation of the emergency running properties. Theingredients are readily biodegradable and develop a good cleaningeffect.

So far as their performance properties are concerned, the lubricantcombinations according to the invention show a very high coefficient offriction, minimal foaming, a good cleaning effect and high compatibilitywith the skin. In addition to the positive properties mentioned, thefollowing boundary conditions are satisfied: moderate foaming improvesthe lubricating effect in problem zones, such as rotary tables,changers, etc.; high substantivity and hence high lubricity, even underadverse operating conditions (for example underconveyor lubrication);low toxicity; generally usable despite inadequacies of equipment; goodcleaning effect;

high capillary activity and film formation on surfaces;

effective, even in the presence of organic impurities and acids oralkalis, and non-corrosive, even in the form of a concentrate;unaffected by beverages.

When used in the beverage industry, the lubricant combinations accordingto the invention—in contrast to the chain lubricants hitherto used—areboth independent of water quality and low-foaming, stable in storage atlow temperatures, non-corrosive and particularly compatible with theenvironment and with the skin.

The compounds corresponding to general formula (I) to be used inaccordance with the present invention may contain one of the followingalkyl groups as the substituent R¹: hexyl, heptyl, octyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl,heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl or docosyl. Thecorresponding mono- or polyunsaturated groups or the correspondingbranched isomers are equally suitable. In addition, the above-mentionedgroups may even be substituted by hydroxy, amino, imino, carbonyl,halogen (preferably chlorine atoms) or carboxyl groups. According to theinvention, preferred compounds corresponding to general formula (I) arethose which contain a linear, saturated or unsaturated alkyl groupcontaining 8 to 18 carbon atoms and, more particularly, 10 to 18 carbonatoms as the substituent R¹.

In another preferred embodiment of the invention, the substituent R² inthe general formula is the group —(CH₂)_(n)—COOM, where n and M are asdefined above. In other words, the nitrogen atom of the fatty aminegroup is alkylated twice by identical groups.

The index “n” in general formula (I) is an integer of 1 to 6.Accordingly, the group mentioned is a methylene, ethylene, propylene,butylene, pentylene or hexylene group, and preferably the index “n” hasa value of 2 or 3. Particular significance is attributed in this regardto the ethylene group (n=2). In another preferred embodiment of theinvention, M is hydrogen or an alkali metal atom, preferred alkalimetals being sodium or potassium, more particularly sodium.

Mixtures of compounds corresponding to general formula (I) may of coursealso be used in accordance with the invention. Examples of compoundscorresponding to formula (I) suitable for use in accordance with theinvention are sodium N-lauryl iminodipropionate, sodium N-cocosalkyliminodipropionate or sodium N-oleyl iminodipropionate. These compoundsmay be prepared in accordance with U.S. Pat. No. 3,574,100. In addition,they are also commercially available, cf. for example DERIPHAT® 160C, aproduct of Henkel KGaA, Duesseldorf, Germany.

The choice of the organic carboxylic acid(s) is not critical providingclear solubility in water is guaranteed under the prevailing conditions.Accordingly, in one preferred embodiment of the present invention, theorganic carboxylic acid is selected from acetic acid, citric acid andglycolic acid, particular significance being attributed to acetic acid.

Preferred chain conveyor lubricants contain 0.01 to 95% by weight of thecompounds corresponding to general formula (I) and 5 to 50% by weight ofthe organic carboxylic acids. In this form, therefore, the chainconveyor lubricants may be obtained free from water. In one particularlypreferred embodiment of the present invention, the chain conveyorlubricants contain 5 to 25% by weight of compounds corresponding togeneral formula (I) and 10 to 15% by weight of organic carboxylic acids.Besides water, the chain conveyor lubricants according to the inventionmay optionally contain other auxiliaries and/or additives as additionalingredients.

Suitable additives for the lubricant combinations according to theinvention are primarily secondary and/or tertiary amines and/or salts ofsuch amines as described in DE-A-39 05 548 cited above.

If desired, the lubricants according to the invention may also containthe N-fatty alkyl-β-aminopropionates described in U.S. Pat. No.3,574,100 cited above. Reference is also made in this regard to EP-A-0372 628 which likewise discloses corresponding N-alkyl aminocarboxylicacids, but in a broader form. Compounds such as these may also be usedas additives in the lubricants according to the invention.

The additives in question, which may optionally be incorporated in thelubricants according to the invention, are generally used in quantitiesof 0 to 10% by weight and preferably in quantities of 1 to 5% by weight,based on the formulation as a whole.

In addition, the lubricant combinations according to the invention maycontain as auxiliaries solubilizers for obtaining a homogeneous in-usesolution with clear solubility in water. Examples of such solubilizersare alcohols, polyalcohols, ethers or polyethers, more particularlyisopropanol, butyl glycol, butyl diglycol or ethylene glycol ether. Thequantity of solubilizer to be used in each individual case is determinedby the betaine used; in each individual case, the expert will determinethe necessary quantity of solubilizer by trial and error. Additions ofsolubilizer of 1 to 20% by weight, based on the formulation as a whole,will generally be sufficient.

According to the invention, other suitable auxiliaries are anionic ornonionic surfactants, for example alkoxylated fatty amines, fattyalcohols, alkoxylated fatty alcohols and also alkyl benzenesulfonatessoluble in hydrophilic solvents. These surfactants are capable ofimproving the wetting of the chains and plate-type conveyor belts shouldthis be necessary in any individual case. In general, additions ofsurfactant of 1 to 10% by weight, based on the formulation as a whole,will be sufficient. Nonionic surfactants, preferably fattyalcohol/ethylene oxide or propylene oxide adducts, more particularlyC_(12/14) fatty alcohol 5EO/4PO adducts, are preferably used.

According to the invention, biocides may also be used as auxiliaries.The biocides used in accordance with the invention may be selected inparticular from quaternary ammonium compounds (QUATS) which contain atleast one long-chain alkyl group, more particularly with 8 to 16 carbonatoms, and/or at least one benzyl group optionally substituted byhalogen atoms. Cocosalkyl dimethyl benzyl ammonium chloride (DODIGEN®226, a product of Bayer AG) is mentioned as an example of such abiocide. In addition, compounds of the alkyl amino-ethylene glycine typecontaining an alkyl group with 6 to 22 carbon atoms and moreparticularly 10 to 16 carbon atoms and, preferably, two aminoethylenegroups are mentioned as preferred biocides. Compounds of this type arealso known as TEGO ampholytes and are marketed, for example, byGoldschmidt AG. (N-Dodecyl-bis-(aminoethylene))-N′-glycine (TEGO®51B, aproduct of Goldschmidt AG) is mentioned as an example of such a biocide.The biocides are generally added to the lubricants according to theinvention in quantities of 0 to 10% by weight and more particularly inquantities of 1 to 5% by weight, based on the formulation as a whole.

If necessary, foam inhibitors may also be added to the lubricantsaccording to the invention as further auxiliaries. Suitable foaminhibitors are, for example, addition products of ethylene oxide andpropylene oxide with fatty alcohols and, in particular, end-capped fattyalcohol polyethylene glycol ethers.

The lubricant combinations according to the invention preferably have apH value in the range from 3 to 6. If the pH value of the chain conveyorlubricant is not already in this range, it may be adjusted to therequired value by addition of an acid, preferably an organic carboxylicacid, as defined above, for example with acetic acid.

In the interests of optimal dosing, the lubricant combinations have adynamic viscosity of less than 300 mPa.s, preferably less than 150 mPa.sand more preferably in the range from 5 to 100 mpa.s, as measured at 20°C. There is generally no need for the viscosity to be separatelyadjusted to the values mentioned. If necessary, however, it may beadjusted to those values by addition of suitable quantities of thepreferred diluent, water, or a solubilizer.

Where the lubricants according to the invention do not consist solely ofcompounds corresponding to general formula (I) and organic carboxylicacids, they may be prepared simply by mixing these components withwater, optionally with addition of the additives and/or auxiliariesmentioned.

Finally, the present invention relates to the use of the chain conveyorlubricants described above as lubricants in the food industry, moreparticularly for automatic chain conveyor installations. For thisapplication, the chain conveyor lubricants according to the inventionare generally diluted with water. The resulting in-use solutions inwater generally contain 0.01 to 1% by weight of compounds correspondingto general formula (I), preferably 0.01 to 0.2% by weight and morepreferably 0.02 to 0.04% by weight of such compounds. The quantities oforganic carboxylic acid to be used can be worked out from the quantityof compounds corresponding to general formula (I) simply by convertingthe quantities of concentrate.

In contrast to standard soap products, the products according to theinvention do not cause any stress cracking and, accordingly, may readilybe used for PET and PC containers (PET=polyethylene terephthalate,PC=polycarbonate) providing no surfactants which cause stress crackingin such materials are used as auxiliaries.

EXAMPLES

The invention is illustrated by the following Examples. Examples 1 to 9according to the invention show formulations of lubricant concentratesand various performance data relating to the corresponding diluteaqueous in-use solutions, these solutions containing the respectiveconcentrates in a quantity of 0.4% by weight. The performance datadetermined (coefficient of friction, foaming behavior, clear solubilityin cold water and emergency running time) are explained in thefollowing.

Examples 1 to 5 are Comparison Examples

In the following formulation examples, all percentages are by weight.

The tests for measuring resistance to friction (hereinafter referred toin short as the “friction coefficient”) were carried out under thefollowing conditions on a pilot-scale bottle conveyor:

Measurement of the friction coefficient of 20×0.5 liter “Euro” beerbottles filled with water as tensile stress using a dynamometer.

Speed of bottle conveyor: approx. 1 m/s

Spraying of the bottle conveyor with 0.4% by weight conveyor lubricantsolution as specified in the Examples.

Spraying capacity of the nozzles: 4 l/h, one nozzle per conveyor.

The friction coefficient “μ” shown in the following is the quotient ofthe measured tensile stress for a bottle to the weight of the bottle ingrams.

In addition, the products were tested with hard water (16° d) inaccordance with the provisions of DIN 53 902.

Foaming behavior is classified as follows:

0=foam-free

1=occasional foam bubbles

2=slight foaming, not troublesome

3=foaming, troublesome

4=intensive foaming, unacceptable, foam under the conveyor

For adequate lubrication, the friction coefficient should be less than0.15. If it exceeds 0.15, there is a significant deterioration in thelubricating effect and hence in satisfactory transport.

The clear solubility in water of the in-use solutions should beguaranteed even over prolonged test periods in order to avoid depositsin ball valve filters, nozzles, the spraying and distribution system,the conveyor and the articles being conveyed. A 0.4% by weight solutionin water with a hardness of 16° d was stored for 72 h and then visuallyevaluated.

Foaming should be minimal because excessive foam not only affects theautomatic bottle inspector and factory safety (danger of slipping), itcan also soften labels and enter the as yet uncapped containers. Inaddition, the friction coefficient is adversely affected by excessivefoaming. By contrast, low foaming is of advantage because it ensuresbetter distribution of the lubricant on the conveyor belts.

Under the test conditions which were also used to determine frictioncoefficient and foaming behavior, the dosing of the chain conveyorlubricant was stopped after a running time of 30 minutes. From thismoment on, the bottles are only lubricated by adhering chain conveyorlubricant. The period of time for which lubrication was maintained withno significant deterioration in the friction coefficient was measured.The end of the test (emergency running time) is reached when thefriction coefficient has fallen by 20% from the starting value.

Example 1

15% Sodium N-lauryl iminodipropionate

14% Acetic acid

71% Water

Friction coefficient: μ=0.10, foaming=2

Clear solubility in water: substantially clear

Emergency running time: 20 mins.

Example 2

15% Sodium N-lauryl iminodipropionate

14% Acetic acid

68% Water

3% C₁₂₋₁₄ fatty alcohol ·5 EO/4PO

Friction coefficient: μ=0.10, foaming=1

Clear solubility in water: absolutely clear

Emergency running time: 25 mins.

Example 3

15% Sodium N-lauryl iminodipropionate

13% Citric acid

72% Water

Friction coefficient: μ=0.11, foaming=2

Clear solubility in water: substantially clear

Emergency running time: 15 mins.

Example 4

15% Sodium N-lauryl iminodipropionate

10% Glycolic acid

75% Water

Friction coefficient: μ=0.11, foaming=1

Clear solubility in water: substantially clear

Emergency running time: not tested

Example 5

86% Sodium N-lauryl iminodipropionate

14% Acetic acid

Friction coefficient: μ=0.10, foaming=1

Clear solubility in water: substantially clear

Emergency running time: 20 mins.

Example 6

15% Sodium N-lauryl iminodipropionate

14% Acetic acid

68% Water

3% Cocosalkyl dimethyl benzylammonium chloride

Friction coefficient: μ=0.10, foaming=1

Clear solubility in water: absolutely clear

Emergency running time: 25 mins.

Example 7

15% Sodium N-lauryl iminodipropionate

14% Acetic acid

68% Water

3% (N-dodecyl-bis-(aminoethylene))-N′-glycine

Friction coefficient: μ=0.10, foaming=1

Clear solubility in water: absolutely clear

Emergency running time: 20 mins.

Example 8

15% Sodium N-cocosiminodipropionate

14% Acetic acid

68% Water

3% Cocosdimethyl benzylammonium chloride

Friction coefficient: μ=0.12, foaming=0

Clear solubility in water: absolutely clear

Emergency running time: 20 mins.

Example 9

15% Sodium N-cocosiminodipropionate

1% Sodium N-oleyl iminodipropionate

14% Acetic acid

68% Water

3% Cocosdimethyl benzylammonium chloride

Friction coefficient: μ=0.11, foaming=0

Clear solubility in water: absolutely clear

Emergency running time: 20 mins.

Comparison Example 1

(Soap-containing chain lubricant)

59% Water

10% Butyl diglycol

15% Fatty acid (oleic/linoleic)

9% Ethylenediamine tetraacetate Na4

4% Monoethanolamine

3% Potassium hydroxide

Friction coefficient: μ=0.12, foaming: 3-4

Clear solubility in water: forms a clear solution in water in aconcentration of 1% up to 12.5° d

Emergency running time: 5 mins.

Comparison Example 2

(Alkylamine-based chain lubricant)

4% N,N-Dimethyl-N-lauryl ammonium acetate

8% Lauryl propylene diammonium acetate

88% Water

Friction coefficient: μ=0.10, foaming=1

Clear solubility: opaque

Emergency running time: approx. 7 mins.

Comparison Example 3

(U.S. Pat. No. 3,574,100)

15% N-Cocosalkyl aminopropionic acid

85% Water

Friction coefficient: μ=0.14, foaming behavior=2

Clear solubility: opaque

Emergency running time: 10 mins.

Comparison Example 4

(U.S. Pat. No. 3,574,100)

15% N-Cocosalkyl aminopropionic acid

3% Lauryl ether phosphoric acid ester

82% Water

Friction coefficient: μ=0.13, foaming=4

Clear solubility in water: opaque

Emergency running time: 7 mins.

Comparison Example 5

15% Sodium-N-lauryl iminodipropionate

85% Water

Friction coefficient: 0.12, foaming=2

Clear solubility in water: opaque

Emergency running time: 15 mins.

What is claimed is:
 1. A water-free conveyor lubricant which forms clearsolutions in water consisting of: a) from 0.01 to 95% by weight of atleast one compound corresponding to formula (I):

 in which R¹ is a saturated or mono- or polyunsaturated, linear orbranched alkyl group containing 6 to 22 carbon atoms, which mayoptionally be substituted by an —OH, —NH₂, —NH—, —CO—, halogen or acarboxyl group, R² is a carboxyl group containing 2 to 7 carbon atoms, Mis hydrogen, alkali metal, ammonium, an alkyl group containing 1 to 4carbon atoms or a benzyl group, and n is an integer of 1 to 6; b) from 5to 50% by weight of at least one organic carboxylic acid selected frommonobasic or polybasic, saturated or mono- or polyunsaturated carboxylicacids containing 2 to 22 carbon atoms; c) at least one solubilizerselected from the group consisting of alcohols, polyalcohols, ethers,and polyethers; d) a nonionic surfactant or an anionic surfactant; e) abiocide selected from the group consisting of a quaternary ammoniumcompound and/or an alkyl aminoethylene glycine; and f) a foam inhibitor.2. The lubricant of claim 1 wherein in formula I the R² group is thegroup —(CH₂)_(n)—COOM in which n and m are as defined therein.
 3. Thelubricant of claim 1 wherein in formula I, n=2 or
 3. 4. The lubricant ofclaim 2 wherein in formula I the n integers are both either 2 or
 3. 5.The lubricant of claim 1 wherein in formula I, n=2.
 6. The lubricant ofclaim 1 wherein in formula I, R¹ is a linear, saturated or unsaturatedalkyl group containing 8 to 18 carbon atoms.
 7. The lubricant of claim 6wherein R¹ contains 10 to 18 carbon atoms.
 8. The lubricant of claim 1wherein component b) is at least one acid selected from the groupconsisting of acetic acid, citric acid and glycolic acid.
 9. Thelubricant of claim 1 wherein component b) is acetic acid.
 10. A methodfor lubricating a chain used in the food and beverage industrycomprising applying to said chain a lubricating quantity of an aqueoussolution of a chain lubricant consisting of: a) 0.01% to 1% by weight ofat least one compound corresponding to formula (I):

 in which R¹ is a saturated or mono- or polyunsaturated, linear orbranched alkyl group containing 6 to 22 carbon atoms, which mayoptionally be substituted by an —OH, —NH₂, —NH—, —CO—, halogen or acarboxyl group, R² is a carboxyl group containing 2 to 7 carbon atoms, Mis hydrogen, alkali metal, ammonium, an alkyl group containing 1 to 4carbon atoms or a benzyl group, and n is an integer of 1 to 6; b) atleast one organic carboxylic acid selected from monobasic or polybasic,saturated or mono- or polyunsaturated carboxylic acids containing 2 to22 carbon atoms; c) at least one solubilizer selected from the groupconsisting of alcohols, polyalcohols, ethers, and polyethers; d) anonionic surfactant or an anionic surfactant; e) a biocide selected fromthe group consisting of a quaternary ammonium compound and/or an alkylaminoethylene glycine; and f) a foam inhibitor.
 11. The method of claim10 wherein the lubricant is applied to an automatic chain conveyor. 12.The method of claim 10 wherein in the compound of formula I the R²groupis the group —(CH₂)_(n)—COOM in which n and M are as defined therein.13. The method of claim 10 wherein in the compound of formula I, n=2 or3.
 14. The method of claim 10 wherein in formula I the n integers areboth either 2 or
 3. 15. The method of claim 10 wherein in the compoundof formula I, R¹ is a linear, saturated or unsaturated alkyl groupcontaining 8 to 18 carbon atoms.
 16. The method of claim 10 wherein inthe chain lubricant, component b) is at least one acid selected from thegroup consisting of acetic acid, citric acid and glycolic acid.